Demon of Skulls

Demon of Skull's power and toughness are equal to the number of skeletons you control plus 4.
On your upkeep, sacrifice Demon of Skull unless you reveal a skeleton card from your hand.
{b}{t}: Target player loses the game. Activate this ability only if you control 20 or more skeletons.
Brought forth by the necromantic energy emitted by the skeletons, he has come once again to feed.